Two subspecies have been proposed (Groves 2001), but results from recent genetic research seem to indicate the presence of both subspecies at Mantadia National Park, supporting the opinion that the two major colour forms are merely part of a clinal variation and not indicative of distinct taxa.

A predicted population reduction of ≥80% in the future over a three generation time period (36 years) for this species is based on a continuing and projected decline in area, extent and quality of habitat, in addition to continuing and projected exploitation through unsustainable hunting pressure. Based on these premises, the species is listed as Critically Endangered.

This highly distinctive lemur is endemic to the island of Madagascar where it inhabits the eastern rain forests from Anjanaharibe-Sud and Antohaka Lava (15 km SE of Andapa) in the north, south to Anosibe An-ala Classified Forest. It has not been found on the Masoala Peninsula or in Marojejy (Mittermeier et al. 2008). It usually occurs at low elevations, but ranges up to 1,800 m (Goodman and Ganzhorn 2004).

Population densities are low, typically ranging from 5.2–22.9 per km2 (Powzyk and Thalmann 2003) or 6.9–13.2 per km2 (C.Golden pers. comm.). A reasonable estimate would be a total of 1,000–10,000 individuals. Population figures are in decline due to habitat destruction and hunting.

The Indri inhabits tropical moist lowland and montane forests. It lives in groups of two to six individuals, normally consisting of a monogamous adult pair (they seek new partners only after a mate dies) and their offspring. Groups in fragmented habitat tend to be larger than those in more extensive, undisturbed areas (Pollock 1979, Powzyk 1997). The diet consists primarily of immature leaves supplemented by flowers, fruit, seeds and bark, which vary in proportion according to season. They occasionally descend to the ground to eat earth, perhaps to detoxify seeds that have also been consumed (Powzyk 1997, Britt et al. 2002, Powzyk and Thalmann 2003). Home ranges average 18 ha in the fragmented forests of Analamazaotra, but have been estimated as large as 40 ha in the more pristine forests of Mantadia. Daily path lengths average 350 m per day (Powzyk, unpublished data). Females give birth every two to three years. Reproduction is highly seasonal, with the birth of a single offspring occurring in May or June. Reproductive maturity is reached between seven and nine years of age (Pollock 1977). Both males and females disperse and the sex ratio at birth is approximately 1:1 (Kappeler 1997).

Illegal hunting is a major problem for the Indri in certain areas. Although long thought to be protected by local fadys (traditional taboos), these do not appear to be universal and the animals are now hunted even in places where such tribal taboos do exist. In many areas these taboos are breaking down with cultural erosion and immigration, and local people often find ways to circumvent taboos even if they are still in place. For example, a person for whom eating the indri is forbidden may still hunt the animals for sale to others, while those who may be forbidden to kill indris can purchase them for food. Recent studies of villages in the Makira Forest indicate that indri have also been hunted in the past for their skins (which were worn as clothing), that indri meat is prized and fetches a premium price, and that current levels of indri hunting are unsustainable (Golden 2005, 2009; Jenkins et al. 2011; R. Dolch pers. comm.).

The principal threat to this species is habitat destruction for slash and burn agriculture, logging and fuelwood gathering, all of which take place even within protected areas. Increasing levels of illegal hunting is also a major problem for the Indri (Jenkins et al. 2011). Fady against the hunting of indri are becoming less respected, and hunting has thus worryingly increased since the political crisis, now posing a serious threat to this species.

This species is listed on Appendix I of CITES. It occurs in three national parks and one pending protected area (Mananara-Nord, Mantadia and Zahamena, and Makira Protected Area), two nature reserves (Betampona and Zahamena) and five special reserves (Analamazaotra, Mangerivola, Ambatovaky, Anjanaharibe-Sud, and Marotandrano) (Mittermeier et al. 2008). The corridors between Mantadia and Zahamena is being proposed as a Conservation Site. Anosibe An -ala Classified Forest in the south should be proposed as a protected area. A major region wide conservation education campaign to eliminate hunting, with the Indri as the flagship species, is recommended. This species has never successfully been kept in captivity and thus captive breeding programs are highly doubtful.

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and Management Conservation sites identified:Yes, over entire range Occur in at least one PA:YesIn-Place Species ManagementIn-Place Education Included in international legislation:Yes Subject to any international management/trade controls:Yes